1. Field of Invention
The invention relates to a sports utility and, in particular, to a sports utility whose pedals can perform independent vertical and horizontal motions with two degrees of freedom.
2. Related Art
Please refer to U.S. Pat. No. 7,651,444, which discloses a sports machine shown in FIG. 11. It includes a frame 9 whose front end has a vertical support 91. The rear end of the frame 9 has a driving wheel 92. Both sides of the driving wheel 92 have a crank 93, respectively. Both sides of the support 91 are pivotally installed with a swinging arm 94, respectively. The bottom end of each of the swinging arms 94 pivotally connects to one end of a pedal bar 95, respectively. The other end of the pedal bar 95 pivotally connects to the corresponding crank 93. Therefore, when the two swinging arms 94 make an alternating motion in the forward and backward directions on the frame 9, the pedal bars 95 are driven by the swinging arms 94 and the cranks 93 to perform running-like actions.
Moreover, in the sports machine both sides of the two pedal bars 95 are provided with a sliding rail 951, respectively. A pedal 96 is installed on each of the sliding rails 951 of the pedal bars 95 in a sliding way. The pedal 96 is pivotally connected with a connecting bar 97, whose other end is pivotally connected to the support 91. The connecting bar 97 is installed with a sliding sheath 971 in a sliding way. Both ends of a movable connecting bar 972 are pivotally connected to the sliding sheath 971 and the swinging arm 94. When the two swinging arms 94 swing alternately back and forth on the frame 9, the pedal bars 95 are driven to make running motions. Moreover, the connecting bars 97 and the movable connecting bar 972 together let the pedals 96 slide back and forth on the sliding rails 961 of the pedal bars 95. This increase the step span of the running, thereby enhancing the exercising effect.
Although the pedals 96 in the conventional sports machine can have upward and downward displacements with the pedal bars 95 and have back and forth displacements as the pedal bars 95 slide, the sliding motion of the pedals 96 is correlated with the upward and downward motion. This is because the connecting relation between the connecting bars 97 and the movable connecting bars 972, and the support 91 and the swinging arms 94. That is, as the pedals 96 are driven by the pedal bars 95 to move up and downs, they are also driven by the connecting bars 97 and the movable connecting bars 972 to move back and forth along the pedal bars 95. As a result, if some component of the sports machine is out of order, e.g. some pivotal part does not have sufficient lubrication or any connecting bar is deformed or broken, then the other normal components thereof will be damaged too if one keeps using the machine. This will increase the repair and maintenance costs.